Preparation of acrylic acid

ABSTRACT

Acrylic acid is prepared by oxidizing propylene with air in the presence of water and a platinum, rhodium, rutheniun or palladium metal catalyst at a temperature above 50* C. and a pressure exceeding 5 bars gauge. A supported palladium catalyst is preferred. Acrylic acid is obtained in about 60 percent yield based on propylene converted and the small amounts of acrolein obtained may be oxidized to acrylic acid.

United States Patent [72] Inventors Reginald David;

Jean Estienne, both of Lyon, France [2]] Appl. No. 826,298 [22] Filed May 20, 1969 [45} Patented Nov. 30, 1971 [73] Assignee Rhone-Poulenc S.A.

Paris, France [32] Priority May 21, 1968 [3 3 France [3! 152605 [54] PREPARATION OF ACRYLIC ACID 7 Claims, No Drawings [52] 0.8. Cl 260/533 N, 260/604 AC [51] Int. Cl C07c 57/04 [50] Field of Search 260/533 N,

[56] References Cited FOREIGN PATENTS 1,428,957 3/1965 France 260/604 AC 904,304 8/ I962 United Kingdom 260/533 N Primary Examiner-Lorraine Av Weinberger Assistant Examiner-Richard D. Kelly Attorney-Cushman, Darby & Cushman ABSTRACT: Acrylic acid is prepared by oxidizing propylene with air in the presence of water and a platinum, rhodium, rutheniun or palladium metal catalyst at a temperature above 50 C. and a pressure exceeding 5 bars gauge. A supported palladium catalyst is preferred. Acrylic acid is obtained in about 60 percent yield based on propylene converted and the small amounts of acrolein obtained may be oxidized to acrylic acid.

PREPARATION OF ACRYLIC ACID acrylic acid by the usual methods. The unconverted propylene can be recycled to the oxidation zone. The present invention relates to a/p ocess for [he prepara- The examples which fOllOW illustrate the invention.

tion of acrylic acid by the oxidation of propylene.

Several processes for the oxidation of propylene to acrylic 5 EXAMPLE 1 acid y air of y oxygen in the 8 Phase have been desuihed- Two-hundred cm. of water and 10.6 g. of a catalyst consist- The commonly used Catalysts are based on some form of ing of palladium deposited on carbon block (palladium conmolybdenum, for example the tfiOXide, which is frequently tent: 10 percent are introduced into a 1 litre stainless steel ausociated with an Oxide Of a polyvalen tal u h 35 Cobalt, toclave. The apparatus is closed and flushed with nitrogen, nickel or tin. These catalysts are generally used in the 10 and then introduced into an oven arranged on a vibratory presence of acid Pl'Om l r h as boron, ph ph agitator and charged with 42.6 g. of propylene (corresponding vanadium, tellurium or arsenic oxide. Such processes have toapressure of ll bars).

been described in British Pat. specifications Nos. 893,077, The temperature of the contents of the autoclave is raised to 961,468, 967,241 and 971,666. Regardless of the catalyst 90 C., with agitation, in l hour 40-minutes. The pressure is d, hi h temperatures, f h order f 300 t 700 C,, are then 30 bars. Air is introduced until a pressure of 100 bars required. Further more, as emerges from French Pat. No. (corresponding to an air pressure of 70 bars) is established. 1,433,572, the catalyst must meet certain conditions as to After 2 hours 15 minutes the pressure becomes stable at 84 compositionsothat acrylic acid is formed preferentially and at bars. The agitation is stopped and the contents of the authe expense of the acrolein which is formed in varying toclave are cooled to 20C. The gas is removed from the apamounts during the oxidation of propylene. Thus the catalyst params through a bubbler containing hydroxylamine has t be careful y p p hydrochloride and then through a bubbler containing 5 N The present invention provides a process for preparing potassium h d id l i acrylic acid which compl'lses oxldlzmg P'Opyiene The reaction medium is withdrawn from the autoclave, and

molecular oxygen ora gas containing molecular oxygen in the to it the 150 cm3of water used to rinse the apparatus are preiienfie of water and of a noble metal of group of the added. This mixture is distilled under normal pressure and Penodlc Table i a temperature above 50 and under 3 cm of a fraction boiling below 99 C., which consists of an pressure exceeding 5 bars gauge aqueous distillate containing various carbonyl compounds, are

Suitable noble metals include platinum, rhodium, ruthenium, and particularly palladium. The metal may be used in a 3 fsg zgzt g acldcomammg res'due ls filtered to remove finely divided state or can be deposited on a carrier such as for Analysis and determination of the Products contained in the example alumina, silica gel, aluminum oxide or aluminum silicate, pumice, active charcoal or bentonite. in this latter case aqueous dlsuuate m the dlsnnanon residue and m the traps it is advantageous to use catalysts containing 1 to 20 percent gave the followmg results:

by weight of metal based on the total weight of carrier and metal; these limits are, however, not essential. The amount of iz 3:332:

catalyst to be used may vary within wide limits depending on Amy, acid 7: 231 2 the reaction conditions. Thus the amount of catalyst expresed a; metallrnay vagy from 0.01 to 10 percent by weight based on 0 The yieds based on propylene convened during the reac e reac ion me rum.

tion, are 16.3 percent CO 6.7 percent acrolein and 58.4 percent acrylic acid. The remainder of the propylene has been converted to various carbonyl and carboxylic compounds.

The reaction temperature may vary within wide limits but the high temperatures required in. the previously known processes are not necessary. in general temperatures between and 200 C., and preferably between and I20 C. are

suitable 45 EXAMPLES 24 The process 15 carried out under gauge pressures greaterthan 5 bars (i.e. an absolute pressure greater than 6 bars), The procedure described in example 1 is followed except preferably 20 to 150 bars gauge. The pressure has no critical that an air pressure of 50 bars is used. By varying the temperaupper limit but for technical and economic reasons, very high ture the results shown in the table below were obtained. The pressures are not of interest. yields are expressed based on the propylene converted.

Acrolein Acrylic acid 002 Tempcr- Propylene ature introduced Yield, Yield, Yield, Examples in 0. Duration in g. g. percent g. percent g. percent 2 3 hrs. 45 min 41.5 0. 49 8.7 4.17 68.3 1.09 16.3 1 hr. 30 min 41 0. 47 5.9 3. 71 54. 7 1. 20 18.9 1 hr 42. 6 0. 23 5 3. 40 56 1.26 22. 2

The relative proportions of propylene and oxygen may vary 60 EXAMPLES 5 and 6 widely but for safety reasons explosive mixtures must be avoided and therefore in practice a large excess of propylene is usually used.

The procedure described in example 1 is followed using a temperature of 90 C., but varying the air pressure; the following results were obtained:

Acrolein Acrylic acid 00 Pressure Propylene of air introduced Yield, Yield, Yield, Examples in bars Duration in g. g. percent g. percent 1. percent 50 1 hr. 30 min 41 0. 47 8.9 3. 71 54.7 1.20 18.0 60 2 hrs 43.2 0. 46 6.0 4.02 53.5 1.44 17.8

The process of this invention may be carried out continu EXAMPLE 7 ously or discontinuously in any type of apparatus usually used for such a process. As well as the acrylic acid obtained in Th Same C n l n as tho e de cribed in example l are about 60 percent yield based on the propylene converted, used except that the catalyst on carbon black is replaced by a acrolein in less than l0 percent yield is formed. This acrolein, catalyst on alumina, containing 10 percent by weight of palafter separation from the acrylic acid, may be oxidised to ladium metal.

The following results were obtained:

Acrylic acid 7.65X 10" mol (5.50 g.) Acrolein 0.86Xl' mol (0.48 g.) CO, 7.54X l0" mol L69 1.)

The yields, based on the propylene converted during the reaction, are 60.7 percent acrylic acid, 6.8 percent acrolein and 20 percent C0,.

EXAMPLES 8 TO 11 The procedure described in Example 1 is followed using a series of catalysts. The results obtained are shown in the table below:

Degree 0! convefrsion Acrolein Acrylic acid Saturated acids CO:

0 propylene, Mol, Yield, Yield. M01, Yield, Yield, Example Catalyst Duration percent )(10- percent l g. percent l XlO- percent Litres percent 8 10% Pd on silica gel 3 hrs. 15 min.... 16. 9 1 6 8. 17 67. 7 1.50 8. 9 1.52 13. 9 10% Pd on silica-alumina 4 hrs. min 12.1 0. 94 7. 2 6. 21 66 1.01 7. 7 1. 38 15. 5 10 7% Pd on silica gel 1 hr. min 13.5 0.42 3. 1 5. 74 59 1.8 13.3 2 21. 9 11 Pd without carrier 2 hrs. 15 mln 13. 1 0. 80 5. 7 5. 65 56. 2 2. 05 14. 7 1. 75 18. 6

1 Based on the propylene converted. 2 1.06 g. 01 Pd metal are used, as catalyst. 5 3.18 g. of Pd metal are used as catalyst.

We laim; 5. A process according to claim 1 wherein the temperature 1. A process for preparing acrylic acid which consists essentially of oxidizing propylene with molecular oxygen or a gas containing molecular oxygen in the'presence of water and of platinum, rhodium, ruthenium or palladium metal catalyst at a temperature above 50 C., and under a pressure exceeding 5 bars gauge.

25 18 50 to C. v

6. A process according to claim 5 wherein the temperature is 70 to C.

to bars. 

2. A process according to claim 1 wherein the metal catalyst is deposited on a carrier.
 3. A process according to claim 2 wherein 1 to 20 percent by weight of metal based on the total weight of metal and carrier is used.
 4. A process according to claim 1 wherein 0.01 to 10 percent by weight of the metal catalyst based on the reaction medium is used.
 5. A process according to claim 1 wherein the temperature is 50* to 200* C.
 6. A process according to claim 5 wherein the temperature is 70* to 120* C.
 7. A process according to claim 1 wherein the pressure is 20 to 150 bars. 